Metal strip and particularly steel strip is cold-reduced by a cold reduction mill having work rolls between which the strip is pulled by a tension reel on which the strip coils. The mill has means for flooding the work rolls and strip with a liquid lubricant for cooling and to faciliate the cold rolling. If this lubricant remains on the strip leaving the work rolls, it forms a lubricant layer between the strip convolutions coiling one on top of another on the reel.
With the strip pulled from the work rolls under tension by the tension reel, the lubricant between the strip convolutions of the coiling strip on the reel can cause the convolutions to suddenly slip in the axial direction of the reel and cause an accident.
Therefore, a set of squeeze rolls is positioned between the work rolls and the reel, so that the strip passes between the rolls to squeeze the lubricant from the strip. Heretofore, the squeeze rolls have been solid cylindrical rolls. The rolls can be cambered or crowned to compensate for roll deflection or bending under the force applied to the ends of the rolls to form a nip having an adequate line pressure to squeeze the lubricant from the strip.
The above technique has not been completely successful, particularly when applied to a Sandzimir mill having work rolls of very small diameter, such as can be exemplified by diameters of from 1 to 21/2". The work rolls and the strip are heavily flooded with a liquid lubricant such as an oil emulsion or palm oil, and the strip tension applied by the reel is very high. If the coil convolutions on the reel suddenly slip axially, a serious accident occurs.
The present invention has resulted from study showing that the liquid lubricant remaining on the strip leaving the work rolls is sometimes unevenly distributed on the strip, causing fluctuation in the squeeze roll's nip line pressure so that all of the lubricant is not squeezed from the strip before the strip reaches the reel.
Furthermore, a Sandzimir mill is a reversing mill having a tension reel on each of its opposite sides, the strip traveling back and forth from one reel to the other as the mill reverses. During reversals, the mill and reels must decelerate to a stop, reverse direction, and then accelerate to full rolling speed. Two sets of squeeze rolls must be used, with one set on one side of the mill and the other on the other side of the mill, the squeeze rolls in each instance being located between the mill's work rolls and the reel. Possibly the temperature fluctuations prevent the maintenance of the desired nip line pressure which the squeeze rolls require to squeeze off the lubricant completely.
A Sandzimir mill is used to cold reduce steels of the harder grades, such as stainless and high silicon steel, and uses extremely high strip tension to facilitate the cold reduction by the small work rolls. Therefore, what might be adequate lubricant removal prior to coiling on the tension reel in other instances, apparently is insufficient to insure firm and slip-free coiling in the case of a Sandzimir mill.